Every token, explained in place
The field strip under the input labels each token with its field and meaning; focus or hover a token to read it. The parser expands ranges, lists and steps into the concrete values it will match, so “*/7” in the minute field shows up as 0, 7, 14 … 56 — and the warning tells you the gap from :56 to :00 is four minutes, not seven.
The example loaded here is a classic surprise. In Vixie cron, when both day fields are restricted the job runs if either matches. But if a day field starts with “*” — as “*/2” does — cron requires both. So 0 0 */2 * 1 runs only on odd-numbered days that are also Mondays. Kubernetes’ parser treats the same text differently. The parser shows which rule it applied and why.
Check a specific date
The Check date tab answers “why didn’t it run on Saturday the 31st?” by testing each field against a date and time you choose and reporting the first field that fails, including the OR/AND decision for the day fields.
Try these
Questions
What does “?” mean in a cron expression?
In Quartz and AWS, “?” means “no specific value” and must appear in exactly one of day-of-month or day-of-week. Kubernetes accepts it as a synonym for “*”. Unix cron rejects it.
Are names like MON and JAN case-sensitive?
No. All supported dialects accept three-letter names in any case. Full names such as MONDAY are rejected by cron parsers (systemd accepts them).